Zombies!

Last night, Neil DeGrasse Tyson did a bit with Jon Stewart on the Daily Show about Zombies, decrying their almost complete impossibility.  So I've been thinking about it:  As an engineer, if I wanted to make a zombie, how would I do it?  I see several levels at which this could work:

Reanimating flesh is problematic.  There are a bunch of physiological and structural failures that occur with death which make using the mechanisms of a cadaver problematic.  However, if the flesh is captured soon enough after (or before) brain death by the zombie mechanism, artificial neural commands could be sent and blood replacement and so forth are perfectly plausible, which would make a human body reasonably functional under control of the zombie mechanism.  Generally a little beyond today's state of the medical art, and if we do get to that state there are a number of huge medical breakthroughs they'd allow (curing paralysis!).  Presumably the zombie mechanism would replace the brain with an artificial counterpart.   (This could explain zombies craving for brains.   It's not so much that they want to eat them, as that they want to remove them and replace them with their own machinery).

You could achieve something that looked like reanimated, long-dead flesh by providing it with an alternate mechanism for motion.  A motorized artificial skeleton comes to mind.  Since the flesh is dead, whatever procedure is used to insert the artificial skeleton is not of consequence to the body.  It just needs to be strong enough to move the body and have sufficient coordination to make the zombies move--like zombies, a pretty low standard.  It's even possible that the rotting protein of the old body could be used as a fuel source for this.

I see several ways such an artificial skeleton could be achieved.  The most obvious would be surgical implantation.  This seems like a lot of work.  If you can do all of this, why not just chase your victims with naked artificial skeletons?  Scary as that would be, zombies (especially if they are the bodies of people who are recognized) would be scarier.  Just covering your artificial skeleton with the skin of the corpses would probably serve fairly well for this need.

Another scheme would be to replace or control just the joints of the corpse to be reanimated. This would require a fairly strong machine, to overcome rigor mortis, but it's probably doable.  It's a little less surgically intrusive, but it's really the same approach as the artificial skeleton.

The animated bug colony creature of the first Men In Black movie suggests yet another alternative--it's similar to the artificial skeleton idea but it provides a practical implementation: the bugs eat the entire flesh and viscera of the victim, leaving only the skin and skeleton.  Then they form a colony, working together to animate the skeleton with the skin around it.

Are zombies possible?  Yes.  Are they likely?  No.  It's hard to imagine an evolutionary advantage to a creature that reproduced this way.  It's just as hard to imagine a purpose for an alien species wanting to do this.